JP2004014543A - Semiconductor manufacturing apparatus and semiconductor device manufacturing method - Google Patents

Abstract

To prevent thermal deformation of a process tube.
A process tube (35) formed of quartz and formed in a cylindrical shape with a closed upper end to form a processing chamber (36) into which a wafer is loaded, a heater (33) laid outside the process tube (35), and a process tube (35). In the hot wall type heat treatment apparatus 10 including the heat equalizing tube 34 laid between the heater 33 and the boat 21 that holds a plurality of wafers W and carries the wafer W into and out of the processing chamber, the process tube 35 has its own weight. A ceiling reinforcing rib 51 and a body reinforcing rib 61 having resistance to thermal deformation are laid.
[Effect] Even if internal viscous flow occurs in the process tube, thermal deformation due to the weight of the process tube can be prevented by the ceiling reinforcing rib and the body reinforcing rib, the life of the process tube can be extended, and the operating cost of the heat treatment equipment can be extended. Can be reduced.
[Selection diagram] Fig. 4

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor manufacturing apparatus, for example, oxidizing or diffusing a semiconductor wafer (hereinafter, referred to as a wafer) on which a semiconductor integrated circuit device (hereinafter, referred to as an IC) is to be formed, and performing carrier activation after ion implantation. The present invention relates to a technique effective for use in a heat treatment apparatus (furnace) for performing heat treatment such as reflow and annealing for planarization.
[0002]
[Prior art]
For a heat treatment such as annealing in an IC manufacturing method, a batch type vertical hot wall heat treatment device (hereinafter, referred to as a hot wall heat treatment device) is widely used. The hot wall type heat treatment apparatus includes a process tube that is formed in a cylindrical shape using quartz and has a closed upper end to form a processing chamber into which a wafer is loaded, a heater laid outside the process tube, and a heater inside the processing chamber. A heat equalizing tube (heat equalizing tube) laid between the process tube and the heater to equalize the temperature and reduce contamination, and hold a plurality of wafers in a state where they are aligned and centered in the processing chamber. A boat for carrying in and out is provided, and a group of wafers on the boat carried into the processing chamber from the furnace port is heated by a heater, so that heat treatment is performed on the group of wafers at one time.
[0003]
The process tube of the conventional hot wall type heat treatment apparatus is formed using quartz because it has few impurities and does not become a contamination source, has a small coefficient of thermal expansion, and has a high transmittance. The ceiling wall of the process tube made of quartz is often formed in a flat plate shape as shown in FIG. 1A or a curved surface shape as shown in FIG. 1B. .
[0004]
[Problems to be solved by the invention]
However, in a process tube made of quartz, when the heat treatment temperature is 900 ° C. or higher, viscous flow starts inside the process tube, and therefore, as shown by an arrow A in FIG. In addition, there is a problem that the body part expands as shown by an arrow B, and the body part shrinks as shown by an arrow C in FIG. Such deformation of the process tube becomes more remarkable as the heat treatment temperature becomes higher, and the internal viscous flow becomes remarkable in a strain point or a gradual cooling point region of 1000 ° C. or more, so that creep deformation due to its own weight may occur. Such deformation is also affected by the composition of the quartz material. Generally, a process tube using synthetic quartz having a lower content of impurities than natural quartz has a high OH group content and a high viscosity, and thus is likely to be deformed.
[0005]
Although it depends on the content of the treatment, since the heat treatment is generally performed in a temperature band around 1200 ° C., the internal viscous flow of the process tube made of quartz is in a state where it can sufficiently occur. When the creep deformation occurs due to its own weight and progresses, damage due to a decrease in the strength of the process tube and damage due to interference with the boat are caused. In particular, when an explosive gas such as hydrogen (H ₂ ) is used, care must be taken because damage to the process tube causes a gas explosion. In addition, when the temperature inside the heater is rapidly increased or decreased in order to shorten the tact time of the hot wall type heat treatment apparatus, a large thermal stress acts on the process tube. Is a problem.
[0006]
The thickness of the process tube is generally 3 mm to 8 mm. Setting this to a large value is advantageous for thermal deformation due to the weight of the process tube made of quartz, but the thermal responsiveness in the processing chamber of the process tube made of quartz is impaired. There is a problem that time becomes long.
[0007]
An object of the present invention is to provide a semiconductor manufacturing apparatus which can extend the life of a process tube, reduce running costs, and have high safety and high operation rate.
[0008]
[Means for Solving the Problems]
A semiconductor manufacturing apparatus according to the present invention is characterized in that the semiconductor manufacturing apparatus is provided with a process tube laid on a body portion so as to extend in a longitudinal direction.
[0009]
According to the above-described means, since the reinforcing rib is laid on the process tube, even if the internal viscous flow of the process tube can occur, it is possible to prevent the thermal deformation of the process tube due to its own weight. Can be.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0011]
In this embodiment, as shown in FIGS. 3 and 4, a semiconductor manufacturing apparatus according to the present invention is a hot-wall type heat-treating apparatus (batch type vertical hot-wall type) for performing a heat treatment step in an IC manufacturing method. (A heat treatment apparatus) 10.
[0012]
The hot wall type heat treatment apparatus 10 shown in FIGS. 3 and 4 includes a box-shaped housing 11 which forms a substantially cubic airtight chamber. A standby chamber 12 is provided to wait for loading / unloading to / from the printer. A boat elevator 13 for raising and lowering the boat 21 is installed in the waiting room 12, and the boat elevator 13 is configured by a feed screw shaft device. That is, the boat elevator 13 is vertically erected on the standby chamber 12 and is rotatably supported on the feed screw shaft 14, a motor 15 installed outside the standby chamber 12 to rotate the feed screw shaft 14, and a feed screw An elevating table 16 that meshes with the shaft 14 and moves up and down with the rotation of the feed screw shaft 14, and a support arm 17 protruding horizontally from the elevating table 16. A seal cap 20 for closing the processing chamber is horizontally supported at the tip of the support arm 17, and the seal cap 20 is constructed in a disk shape substantially equal to the outer diameter of the process tube 35. A boat 21 stands vertically on the center line of the seal cap 20 and is supported via a base 19.
[0013]
The boat 21 includes a pair of end plates 22 and 23 at the top and bottom, and three holding members 24 which are provided between the end plates 22 and 23 and vertically disposed. Are provided with a large number of holding grooves 25 arranged at regular intervals in the longitudinal direction so as to face each other and open. The boat 21 is configured such that the wafers W are inserted between the holding grooves 25 of the three holding members 24 to thereby align and hold the plurality of wafers W horizontally and with their centers aligned. . Between the boat 21 and the seal cap 20, there is arranged a heat insulating cap 26 in which a heat insulating material is sealed. The heat insulating cap 26 supports the boat 21 in a state of being lifted from the upper surface of the seal cap 20. Thereby, the lower end of the boat 21 is separated from the position of the furnace port of the processing chamber by an appropriate distance.
[0014]
A boat loading / unloading port 30 is opened just above the boat 21 on the ceiling wall of the waiting room 12, and a scavenger 31 is constructed on the ceiling wall of the waiting room 12 so as to surround the boat loading / unloading port 30. I have. Above the scavenger 31, a cylindrical heat insulating tank 32 having an upper end closed is arranged concentrically and vertically raised, and a heater 33 made of an electric resistor is spirally provided on the inner periphery of the heat insulating tank 32. It is laid in a shape. The heater 33 is configured to be subjected to sequence control and feedback control by a temperature controller.
[0015]
Inside the heater 33, a heat equalizing tube 34 is arranged concentrically and stands vertically on the scavenger 31, and inside the heat equalizing tube 34, a process tube 35 is arranged concentrically. The heat equalizing tube 34 is made of silicon carbide (SiC) or quartz, has an outer diameter smaller than the inner diameter of the heater 33, is formed in a cylindrical shape having an upper end closed and a lower end opened, and the process tube 35 surrounds the outside. So that they are concentric. The process tube 35 is arranged concentrically at the boat loading / unloading port 30 and is supported by the ceiling wall of the standby chamber 12 of the housing 11. A scavenger is provided between the lower end of the process tube 35 and the lower end of the heat equalizing tube 34. 31 is hermetically sealed.
[0016]
The process tube 35 is made of quartz glass and is formed in a cylindrical shape having an upper end closed and a lower end opened. The hollow portion of the process tube 35 forms a processing chamber 36 into which a plurality of wafers held long and aligned by the boat 21 are loaded, and a lower end opening of the process tube 35 is a furnace for taking in and out the wafer. The mouth 37 is constituted. The inner diameter of the process tube 35 is set to be larger than the maximum outer diameter (for example, three hundred mm) of the wafer to be handled. An exhaust pipe 38 is connected to the lower end of the process tube 35, and the exhaust pipe 38 is connected to an exhaust device (not shown) so that the processing chamber 36 can be exhausted. A gas introduction pipe 39 connected to a gas supply device 40 for supplying a raw material gas, a carrier gas, or the like is inserted into the scavenger 31, and the gas introduction pipe 39 is laid upward along a side surface of the process tube 35. Thus, it is connected so as to communicate with a buffer chamber 41 formed on a ceiling 35 a of the process tube 35. A plurality of gas outlets 42 are opened in the buffer chamber 41 at the ceiling 35 a of the process tube 35, and gas introduced from the gas introduction pipe 39 into the buffer chamber 41 diffuses in the buffer chamber 41, The plurality of gas outlets 42 are blown into the processing chamber 36 in a shower shape. The gas introduced from the group of gas outlets 42 into the upper end of the processing chamber 36 flows down the processing chamber 36 of the process tube 35 and is exhausted by the exhaust pipe 38.
[0017]
As shown in detail in FIG. 5, the process tube 35 is provided with a ceiling reinforcing rib 51 and a body reinforcing rib 61 which are resistant to thermal deformation due to its own weight. The body reinforcing rib 61 is made of quartz of the same quality as the process tube 35 and is formed in a substantially rectangular flat plate shape. The ceiling reinforcement rib 51 is set to have a resistance to the hanging of the ceiling 35a of the process tube 35, and is formed in a flat plate shape having an arc along the curved surface of the ceiling 35a. Are welded at right angles to the surface of the ceiling portion 35a with a substantially constant width and a constant height. The torso reinforcing rib 61 has a large second moment of area so as to have resistance to buckling and longitudinal shrinkage of the torso 35b of the process tube 35, and is formed into four rectangular flat plates. Then, it is welded at a right angle to the outer peripheral surface of the process tube 35 at a position continuous with the four lower ends of the ceiling reinforcing rib 51 on the outer periphery of the body portion 35b of the process tube 35. The lower end position of the body reinforcing rib 61 substantially corresponds to the lower end position of the heater 33. This is for the following reason. Viscous flow occurs at the upper part of the process tube 35 heated by the heater 33, whereas viscous flow does not occur at the lower end of the process tube 35 not heated by the heater 33. As a result, if the body reinforcing ribs 61 are laid so as to straddle a portion having a temperature difference, the body reinforcing ribs 61 are in a state of restraining the thermal expansion of the process tube 35, so that the internal stress is applied to the process tube 35. Will be generated. In order to prevent the generation of internal stress in the process tube 35, it is preferable that the body reinforcing rib 61 is not laid so as to straddle a portion having a temperature difference.
[0018]
Next, an annealing process for manufacturing a defect-free layer (DZ) wafer (hereinafter, referred to as a DZ wafer) as a substitute for an epitaxial wafer using the hot-wall type heat treatment apparatus according to the above configuration will be described with reference to FIG. Will be explained.
[0019]
As shown in FIG. 3, a plurality of wafers W to be annealed from now on are loaded into a boat 21 waiting in the standby chamber 12 by a wafer transfer device (not shown). At this time, since the furnace port 37 of the process tube 35 is closed by the shutter 18, hot air in the processing chamber 36 does not enter the standby chamber 12.
[0020]
When a predetermined number of sheets are loaded, in the boat loading step shown in FIG. 6, the boat 21 is provided by the elevator 13 and is carried into the processing chamber 36 from the furnace port 37 of the process tube 35 (boat loading). As shown in (2), it is placed in the processing chamber 36 while being supported by the seal cap 20. As shown in FIG. 6, the temperature of the processing chamber 36 is maintained at a preset standby temperature of 600 ° C. until the temperature raising step starts.
[0021]
When the boat 21 is placed in the processing chamber 36, the processing chamber 36 is heated by the heater 33, so that the temperature is raised in accordance with the temperature sequence of the temperature raising step shown in FIG. At this time, an error between the target temperature of the sequence control of the heater 33 and the actual temperature increase of the processing chamber 36 is corrected by feedback control.
[0022]
As shown in FIG. 6, when the temperature of the processing chamber 36 reaches 1200 ° C. in the high-temperature processing step set as a suitable temperature for the annealing process, the temperature of the processing chamber 36 is maintained at a constant temperature of 1200 ° C. Is done. At this time, even if internal viscous flow occurs in the process tube 35, since the ceiling reinforcing rib 51 and the body reinforcing rib 61 are laid on the process tube 35, thermal deformation due to the own weight of the process tube 35 does not occur. Will be prevented.
[0023]
As shown in FIG. 6, after 120 minutes, which is the processing time of the preset high-temperature processing step, elapses, the temperature of the processing chamber 36 is lowered according to the temperature sequence of the temperature lowering step shown in FIG. . At this time, the heat capacity of the process tube 35 is increased by the amount of the ceiling reinforcing ribs 51 and the trunk reinforcing ribs 61 laid, but the heat capacity of the ceiling tube 51 and the trunk reinforcing ribs laid on the outer surface of the process tube 35 is increased. Since the ribs 61 perform the same function as the cooling fins, it is possible to suppress the extension of the time for lowering the temperature of the processing chamber 36 of the process tube 35.
[0024]
When the temperature of the processing chamber 36 reaches 600 ° C., which is a preset standby temperature, the temperature is kept constant. When the temperature of the processing chamber 36 becomes the standby temperature, in the boat unloading step, the seal cap 20 is lowered by the boat elevator 13 so that the furnace port 37 is opened, and the processed wafer W held in the boat 21 is held. The group is carried out of the processing chamber 36 to the standby chamber 12. As shown in FIG. 3, when the boat 21 is carried out to the standby chamber 12, the furnace port 37 of the processing chamber 36 is closed by the shutter 18, and the processed wafer W is transferred from the boat 21 by the wafer transfer device. Discharged.
[0025]
In the above annealing step, as shown in FIG. 6, argon (Ar) gas is flowed as an annealing gas at a rate of 10 to 40 SLM (standard liter / minute) from the start of the temperature raising step to the end of the temperature lowering step. .
[0026]
By the way, in the method of manufacturing a DZ wafer by annealing, a hydrogen gas or an argon gas is used as an annealing gas. When hydrogen gas is used, the depth of the defect-free layer can be made larger than when argon gas is used. That is, hydrogen has a reducing action at a high temperature, and reacts with silicon (Si) or an oxide film of a wafer and oxygen (O ₂ ) of quartz to become H ₂ O. At a high temperature, oxygen diffuses from the wafer into the gas phase. By eliminating the oxygen dissolved in silicon as described above, a DZ wafer is manufactured.
[0027]
However, argon gas is used in the method of manufacturing a DZ wafer according to the present embodiment for the following reasons.
1) A DZ wafer can also be manufactured by annealing with an argon gas.
2) Argon gas can reduce equipment costs as compared with hydrogen gas.
3) The argon gas annealing has less contamination than the hydrogen gas annealing. That is, when the process tube made of quartz is shaved by the reducing action of hydrogen gas, the contaminant element in the quartz of the process tube comes out to the gas phase (processing chamber), and the contaminant element that comes out adheres to the wafer. Doing so will contaminate the wafer. On the other hand, since the argon gas, which is an inert gas, does not react with the wafer, the DZ wafer is manufactured by diffusing impurities from the wafer into the gas phase due to the high temperature.
[0028]
According to the present embodiment, the following effects can be obtained.
[0029]
1) By laying the ceiling reinforcing ribs and the trunk reinforcing ribs on the outer surface of the process tube, the mechanical strength of the process tube can be increased, so that even if the internal viscous flow of the process tube may occur. In addition, the occurrence of thermal deformation due to the weight of the process tube can be prevented. As a result, the life of the process tube can be extended, and the running cost of the IC manufacturing method can be reduced.
[0030]
2) By preventing the thermal deformation of the process tube at high temperatures, synthetic quartz, which is conventionally unsuitable for high temperatures due to its high viscosity despite its high purity and low contamination level on the wafer, is used. Can be realized. As a result, the accuracy of the heat treatment can be increased, and the yield and throughput of the IC manufacturing method can be increased.
[0031]
3) Since the ceiling reinforcing ribs and the body reinforcing ribs laid on the outer surface of the process tube perform the same function as the cooling fins, the time for lowering the temperature of the processing chamber of the process tube can be shortened. Tact time of the entire process can be reduced.
[0032]
4) By laying the reinforcing ribs on the ceiling and the trunk on the outer surface of the process tube, the rigidity of the process tube against thermal stress due to the temperature difference between the inner surface and the outer surface of the process tube can be increased. The cooling unit forcibly evacuates the interior of the heater (the space between the heat insulating layer and the soaking tube) to rapidly cool it, thereby reducing the time required to lower the temperature of the processing chamber of the process tube. The tact time of the entire heat treatment process can be further reduced.
[0033]
5) By preventing thermal deformation of the process tube, it is possible to prevent interference with the boat due to damage or deformation of the process tube, thereby avoiding occurrence of secondary disaster due to such damage or interference. Therefore, the safety of the heat treatment process by the hot wall heat treatment device and its operation can be enhanced.
[0034]
6) By making the lower end position of the body reinforcing rib substantially correspond to the lower end position of the heater, a temperature difference was generated between the upper part of the process tube heated by the heater and the lower end part of the process tube not heated by the heater. Even in this case, the torso reinforcing ribs were laid because it is possible to prevent the torso reinforcing ribs from being in a state of restraining the thermal expansion of the process tube and to prevent the internal stress from being generated in the process tube. Therefore, it is possible to prevent adverse effects such as breakage of the process tube.
[0035]
The reinforcing ribs laid on the process tube are not limited to the configuration as in the above-described embodiment, but may be configured as shown in, for example, FIGS.
[0036]
The process tube 35A according to the second embodiment shown in FIG. 7 is different from the first embodiment in that the number of the body reinforcing ribs 61 is reduced to two. The point is that two circular ring-shaped body reinforcing ribs (hereinafter, referred to as reinforcing flanges) 62 are horizontally connected to each other in the axial direction at an intermediate portion in the axial direction of the partial reinforcing ribs 61 at intervals in the axial direction. The two reinforcing flanges 62 serve to prevent the swelling of the body 35b of the process tube and also to prevent the two body reinforcing ribs 61 extending in the vertical direction from falling down.
[0037]
The process tube 35B according to the third embodiment shown in FIG. 8 is different from the first embodiment in that the number of the body reinforcing ribs 61 is increased to six, and the ceiling reinforcing ribs are provided. 51 is omitted.
[0038]
The process tube 35C according to the fourth embodiment shown in FIG. 9 is different from the first embodiment in that the number of body reinforcing ribs 61 is increased to six, and that the six The point that the lower end of the part reinforcing rib 61 is connected to the flange 35c protruding from the lower end of the process tube, and that the ceiling part reinforcing rib 51 is omitted. The six body reinforcing ribs 61 are prevented from falling down by the flange 35c of the process tube connected to the lower end.
[0039]
The process tube 35D according to the fifth embodiment shown in FIG. 10 differs from the process tube 35D according to the first embodiment in that the number of body reinforcing ribs 61 is reduced to two. The point is that a reinforcing flange 62 is horizontally connected to an intermediate portion in the axial direction of the body reinforcing rib 61, the ceiling 35a is formed horizontally, and the ceiling reinforcing rib 51 is omitted.
[0040]
The process tube 35E according to the sixth embodiment shown in FIG. 11 differs from that of the first embodiment in that the number of body reinforcing ribs 61 is reduced to two. The point that the lower end of the body reinforcing rib 61 is connected to the flange 35c of the process tube and connected horizontally, the point that the auxiliary flange 62 is horizontally connected to the axial middle part of the two body reinforcing ribs 61, The point is that the ceiling 35a is formed horizontally, and the ceiling reinforcing rib 51 is omitted.
[0041]
The process tube 35F according to the seventh embodiment shown in FIG. 12 differs from the first embodiment in that the body reinforcing rib 61 and the buffer chamber 41 are omitted.
[0042]
The process tube 35G according to the eighth embodiment shown in FIG. 13 differs from the first embodiment in that the body reinforcing rib 61 and the buffer chamber 41 are omitted, and the ceiling 35a is different from the first embodiment. The point is that it is formed horizontally, and that two substantially rectangular flat plate-shaped ceiling reinforcing ribs 52 are laid in parallel with each other.
[0043]
The present invention is not limited to the above embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention.
[0044]
For example, the annealing gas is not limited to using an argon gas, but may be a hydrogen gas.
[0045]
In addition, the present invention is not limited to use for manufacturing a DZ wafer, but may be used for manufacturing an SOI (silicon on insulator) wafer.
[0046]
The present invention is not limited to the batch type vertical hot wall type heat treatment apparatus, but can be applied to all heat treatment apparatuses such as a vertical type hot wall type reduced pressure CVD apparatus.
[0047]
【The invention's effect】
As described above, according to the present invention, the life of the process tube can be extended, the running cost can be reduced, and the safety and operation rate can be increased.
[Brief description of the drawings]
1A and 1B are front views showing a conventional process tube, in which FIG. 1A shows a process tube having a flat ceiling portion, and FIG. 1B shows a process tube having a curved ceiling portion. .
FIG. 2 is a front sectional view showing thermal deformation of a conventional process tube.
FIG. 3 is a front sectional view showing a state before a boat loading step of the hot wall heat treatment apparatus according to the embodiment of the present invention;
FIG. 4 is a front sectional view showing the heat treatment step.
FIGS. 5A and 5B show a first embodiment of a process tube, wherein FIG. 5A is a plan view and FIG. 5B is a front view.
FIG. 6 is a graph showing a temperature sequence of an annealing step in a method of manufacturing an IC according to an embodiment of the present invention.
7A and 7B show a second embodiment of the process tube, wherein FIG. 7A is a plan view and FIG. 7B is a front view.
FIG. 8 shows a third embodiment of the process tube, wherein (a) is a plan view and (b) is a front view.
9A and 9B show a fourth embodiment of the process tube, wherein FIG. 9A is a plan view and FIG. 9B is a front view.
10A and 10B show a fifth embodiment of the process tube, wherein FIG. 10A is a plan view and FIG. 10B is a front view.
FIGS. 11A and 11B show a sixth embodiment of the process tube, wherein FIG. 11A is a plan view and FIG. 11B is a front view.
FIG. 12 shows a seventh embodiment of the process tube, wherein (a) is a plan view and (b) is a front view.
FIGS. 13A and 13B show an eighth embodiment of the process tube, wherein FIG. 13A is a plan view and FIG. 13B is a front view.
[Explanation of symbols]
W: wafer (substrate), 10: hot wall type heat treatment apparatus (semiconductor manufacturing apparatus), 11: housing, 12: standby room, 13: boat elevator, 14: feed screw shaft, 15: motor, 16: elevating table, 17 Support arm, 18 Shutter, 19 Base, 20 Seal cap, 21 Boat, 22, 23 End plate, 24 Holding member, 25 Holding groove, 26 Heat insulating cap, 30 Boat loading and carrying Outlet, 31: Scavenger, 32: Heat insulation tank, 33: Heater, 34: Heat equalizing tube, 35, 35A to 35G: Process tube, 35a: Ceiling, 35b: Body, 35c: Flange, 36: Processing chamber, 37 ... furnace port, 38 ... exhaust pipe, 39 ... gas introduction pipe, 40 ... gas supply device, 41 ... buffer chamber, 42 ... gas ejection port, 51 ... ceiling reinforcing rib, 52 ... rectangular flat plate-shaped ceiling Strong ribs, 61 ... the body portion reinforcement ribs, 62 ... reinforcing flange (body portion reinforcing ribs).

Claims (5)

A semiconductor manufacturing apparatus comprising: a process tube in which a reinforcing rib is laid on a body to extend in a longitudinal direction. 2. The semiconductor manufacturing apparatus according to claim 1, wherein the reinforcing rib extends from a flange projecting from a lower end of the process tube. 3. The semiconductor manufacturing apparatus according to claim 1, wherein a reinforcing rib protrudes from a closing wall of the process tube. 4. 4. The semiconductor manufacturing apparatus according to claim 1, wherein a plurality of the reinforcing ribs are arranged on a body of the process tube at equal intervals in a circumferential direction. 5. A step in which a boat holding a plurality of substrates is carried into a processing chamber of a process tube laid so as to extend in a longitudinal direction on a reinforcing rib body,
Heating a plurality of substrates carried into the processing chamber by a heater laid outside the process tube;
A step of carrying out the boat holding the heated plurality of substrates from the processing chamber.

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